基于负反馈和有源偏置的宽带低噪放设计

提出一种基于改进型负反馈电路的宽带低噪声放大器.放大器芯片采用0.25 μm GaAs pHEMT工艺设计和SiP技术封装.通过调节封装内芯片外围负反馈电路实现增益平坦度优化，将低噪放工作频带拓展至0.5~2.5 GHz，可有效覆盖GSM、TD-SCDMA、WCDMA、GPS等多个应用频段.片内的稳压及温度补偿有源偏置电路可对供电电压波动及环境温度变化进行有效补偿，以适应复杂工作环境.经测试，低噪声放大器的供电电压为3.3 V，功耗为40 mW，工作频率为0.5~2.5 GHz，带宽高达5个倍频程，带内增益约为14 dB，增益平坦度≤1 dB，噪声系数≤1.3 dB，输入输出回波损耗≤-10 dB，输入三阶交调点≥1 dBm，封装后尺寸为3 mm×3 mm×1 mm.
Abstract: A broadband LNA was presented based on improved negative feedback design. The LNA chip was designed with 0.25 μm GaAs pHEMT technology and packaged in SiP package technique. With the adjustment of the negative feedback circuit around the chip inside the package, the LNA achieved planarized gain and an optimized operating bandwidth from 0.5 GHz to 2.5 GHz, which covered several application bands including GSM, TD-SCDMA, WCDMA and GPS. To guarantee the excellent performance in severe environments, an active biasing was used inside the chip. As results, effective compensations for the fluctuation of the supply voltage and the temperature variation were achieved. It is tested that the broadband LNA shows superior performances within 0.5 GHz to 2.5 GHz, including gain of about 14 dB, gain flatness of less than 1dB, and noise figure of less than 1.3 dB. Test results also show that the input and output return loss is less than -10 dB, the input third-order intercept point is much greater than 1 dBm, and the DC power consumption is 40 mW at 3.3 V supply voltage. The packaged size of this broadband LNA is 3 mm×3 mm×1 mm.